Epidemiologic studies have demonstrated a greater prevalence of essential hypertension (EH) in blacks with a disproportionately greater hypertension-related mortality in blacks. Delineation of mechanisms governing the pathogenesis of EH in blacks could lead to more effective measures of hypertension control, prophylaxis, and prevention in blacks. In a preceding study, we have demonstrated a greater prevalence of sodium (Na) sensitivity in young adult blacks than whites. Blacks have greater urine Na:K ratio. Cardiovascular reactivity is high in some blacks but reactivity is not altered by Na loading. Variations in membrane cation transport correlate with Na sensitivity in blacks. The objective of this program is to investigate the interaction of biobehavioral factors in relation to blood pressure control in a representative young black population (RBS) and a group of young blacks at high risk for EH (borderline hypertensives). The subjects of this project consist of blacks who were enrolled in the Collaborative Perinatal Project (CPP) at birth. These subjects have been studied longitudinally in adolescence, young adulthood, and in a preceding project on biobehavioral factors affecting EH in young blacks. We will investigate the effect of potassium loading on the cardiovascular response to mental stress, and cell membrane cation transport. We will determine if there are behavioral patterns (anger, hostility) which distinguish the RBS and BBH groups, and we will relate these behavioral indices to the biologic parameters. The extensive longitudinal data in this population will be analyzed to develop correlates of the behavioral and biologic factors. The overall hypothesis is: Certain biologic factors (Na:K sensitivity, cation transport) within the black race interact with behavioral factors (reactivity, anger, hostility, social-economic) to elevate the risks for EH.